Hyperoxic Lung Injury Research Articles

Intermittent hypoxia during recovery from neonatal hyperoxic lung injury causes long-term impairment of alveolar development: A new rat model of BPD.

Bronchopulmonary dysplasia (BPD) is a chronic lung injury characterized by impaired alveologenesis that may persist into adulthood. Rat models of BPD using varying degrees of hyperoxia to produce injury either cause early mortality or spontaneously recover following removal of the inciting stimulus, thus limiting clinical relevance. We sought to refine an established rat model induced by exposure to 60% O2 from birth by following hyperoxia with intermittent hypoxia (IH). Rats exposed from birth to air or 60% O2 until day 14 were recovered in air with or without IH (FIO2 = 0.10 for 10 min every 6 h) until day 28 Animals exposed to 60% O2 and recovered in air had no evidence of abnormal lung morphology on day 28 or at 10-12 wk. In contrast, 60% O2-exposed animals recovered in IH had persistently increased mean chord length, more dysmorphic septal crests, and fewer peripheral arteries. Recovery in IH also increased pulmonary vascular resistance, Fulton index, and arterial wall thickness. IH-mediated abnormalities in lung structure (but not pulmonary hypertension) persisted when reexamined at 10-12 wk, accompanied by increased pulmonary vascular reactivity and decreased exercise tolerance. Increased mean chord length secondary to IH was prevented by treatment with a peroxynitrite decomposition catalyst [5,10,15,20-Tetrakis(4-sulfonatophenyl)-21H,23H-porphyrin iron (III) chloride, 30 mg/kg/day, days 14-28], an effect accompanied by fewer inflammatory cells. We conclude that IH during recovery from hyperoxia-induced injury prevents recovery of alveologenesis and leads to changes in lung and pulmonary vascular function lasting into adulthood, thus more closely mimicking contemporary BPD.

Erythropoietin attenuates hyperoxia-induced lung injury by upregulating epidermal growth factor-like domain 7 in newborn rats.

The aim of the present study was to observe the effects of recombinant human erythropoietin (rhEPO) on the expression of epidermal growth factor-like domain 7 (EGFL7) and cell apoptosis in lung tissue following hyperoxic lung injury in newborn rats. The 96 Sprague-Dawley newborn rats were randomly divided into 4 groups (n=24) as follows: Room air-exposed control group, room air-exposed rhEPO-treated group, hyperoxia-exposed group and the hyperoxia-exposed rhEPO-treated group. Pups (n=8) from each group were sacrificed on postnatal days 3, 7 and 14. The pulmonary morphometric and microvessel density changes were observed. In addition, the mRNA and protein expression levels of EGFL7, B-cell lymphoma 2 (Bcl-2) and Bcl-2-like protein 4 (Bax) in lung tissue samples were measured. The rats in the hyperoxia-exposed group exhibited alveolar and pulmonary vascular dysplasia, as well as low mRNA and protein expression levels of EGFL7 and Bcl-2, in addition to high level of Bax in the lung tissue samples when compared with the room air-exposed control group (P<0.05). However, in the hyperoxia-exposed rhEPO-treated group the lung histopathology was improved, and the protein and mRNA expression levels of EGFL7 and Bcl-2 were increased compared with the hyperoxia-exposed group (P<0.05). Furthermore, the expression level of Bax was lower than that of the hyperoxia-exposed group (P<0.05). The present study demonstrated that rhEPO promotes alveolar development and increases pulmonary vascular density by upregulating the expression level of EGFL7 in hyperoxia-induced lung injury of newborn rats.

252 - Synergistic Effects of Aurothioglucose and Hyperoxia in Neonatal Hyperoxic Lung Injury

Oxygen toxicity and antioxidant deficiencies contribute to the development of bronchopulmonary dysplasia (BPD) in preterm infants. We recently demonstrated that a single injection of aurothioglucose (ATG), a thioredoxin reductase-1 (TrxR1) inhibitor, attenuated lung injury and increased Nrf2 activation in a C3H/HeN mouse model of BPD. Nrf2 activation was greatest in ATG-treated hyperoxia-exposed mice. Additional unpublished data in vivo suggests that ATG treatment also enhances endogenous glutathione (GSH) levels. Hyperoxic sensitivity in newborn mice is strain-dependent, therefore we first tested the hypothesis that the protective effects of ATG are strain independent and dose-dependent. C57Bl/6 mice were pre-treated with a single dose of 0, 25 or 50 mg/kg ATG at 4d of life and were subsequently exposed to room air (RA) or hyperoxia (85% O2) from 4- 14d. Histologic analyses of formalin fixed lungs were performed to evaluate lung development. Our data revealed that hyperoxic exposure resulted in lung developmental abnormalities in saline-treated mice. Preliminary qualitative analyses of H&E-stained lung sections revealed dose-dependent attenuation of ATG treatment on hyperoxia-induced lung development with the most robust protective effect observed in mice pretreated with 50 mg/kg ATG. Studies in vitro tested the hypothesis that ATG inhibits TrxR1, protects against hyperoxia-induced anti-proliferative effects in lung epithelial cells, and enhances cellular GSH levels. Murine transformed club cells (mtCCs) were treated with 0 or 5 μM ATG and were exposed RA or hyperoxia (85% O2) for 24 h. For each condition the following was determined: cell counts, TrxR1 activity via insulin-disulfide reductase assay, and glutathione levels via the glutathione reductase recycling assay. ATG treatment increased viable cell numbers in RA-exposed cells, which directly correlated with a 25% decrease in TrxR1 activity. In addition, ATG-treated hyperoxia-exposed cells TrxR1 activity was 50% less than in control-treated cells and was associated with enhanced total GSH levels. In summary, the effects of ATG on hyperoxia-induced lung developmental deficits are dose-dependent and strain-independent. In vitro, our data reveals synergism between ATG and hyperoxia similar our previous observations in C3H/HeN mice. The inverse correlation between the degree of TrxR1 inhibition and ATG-mediated protection elicited by the combination of ATG and hyperoxia suggests a threshold of TrxR1 inhibition necessary for the protective effects of ATG. Future studies will define dose-response characteristics and mechanisms by which ATG is protective in vivo and in vitro with the overall goal of optimizing TrxR1 inhibition as a viable therapeutic strategy to prevent BPD.

Proton-pump inhibitor omeprazole attenuates hyperoxia induced lung injury.

BackgroundThe administration of supplemental oxygen to treat ventilatory insufficiency may lead to the formation of reactive oxygen species and subsequent tissue damage. Cytochrome P4501A1 (CYP1A1) can modulate hyperoxic lung injury by a currently unknown mechanism. Our objective was to evaluate the effect of administration of omeprazole on the induction of CYP1A1 and its influence on hyperoxic lung injury in an established preterm rabbit model.MethodsOmeprazole was administered either (1) directly to the fetus, (2) to the mother or (3) after birth to the pups in different doses (2–10 or 20 mg/kg). Controls were injected with the same amount of saline. Pups were housed in normoxia (21 %) or hyperoxia (>95 %) for 5 days. Outcome parameters were induction of CYP1A1 measured by real-time polymerase chain reaction (RT-PCR) immediately after delivery, at day 3 and day 5 as well as lung function, morphometry and immunohistochemistry assessed at day 5 of life. Transcriptome analysis was used to define the targeted pathways.ResultsDaily neonatal injections demonstrated a dose-dependent increase in CYP1A1. Lung function tests showed a significant improvement in tissue damping, tissue elasticity, total lung capacity, static compliance and elastance. Morphometry revealed a more developed lung architecture with thinned septae in animals treated with the highest dose (20 mg/kg) of omeprazole. Surfactant protein B, vascular endothelial growth factor and its receptor were significantly increased on immunohistochemical stainings after omeprazole treatment.ConclusionsNeonatal administration of omeprazole induces CYP1A1 in a dose-dependent matter and combined pre- and postnatal administration attenuates hyperoxic lung injury in preterm rabbits, even with the lowest dose of omeprazole without clear CYP1A1 induction.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-1009-3) contains supplementary material, which is available to authorized users.

Systematic review and meta-analysis of nasal potential difference in hypoxia-induced lung injury.

Nasal potential difference (NPD), a well-established in vivo clinical test for cystic fibrosis, reflects transepithelial cation and anion transport in the respiratory epithelium. To analyze whether NPD can be applied to diagnose hypoxic lung injury, we searched PubMed, EMBASE, Scopus, Web of Science, Ovid MEDLINE, and Google Scholar, and analyzed data retrieved from eleven unbiased studies for high altitude pulmonary edema (HAPE) and respiratory distress syndrome (RDS) using the software RevMan and R. There was a significant reduction in overall basal (WMD −5.27 mV, 95% CI: −6.03 to −4.52, P < 0.00001, I2 = 42%), amiloride-sensitive (ENaC) (−2.87 mV, 95% CI: −4.02 to −1.72, P < 0.00001, I2 = 51%), and -resistant fractions (−3.91 mV, 95% CI: −7.64 to −0.18, P = 0.04, I2 = 95%) in lung injury patients. Further analysis of HAPE and RDS separately corroborated these observations. Moreover, SpO2 correlated with ENaC-associated NPD positively in patients only, but apparently related to CFTR-contributed NPD level inversely. These correlations were confirmed by the opposite associations between NPD values and altitude, which had a negative regression with SpO2 level. Basal NPD was significantly associated with amiloride-resistant but not ENaC fraction. Our analyses demonstrate that acute lung injury associated with systemic hypoxia is characterized by dysfunctional NPD.

Inhalational mercury toxicity from artisanal gold extraction reported to the Oregon poison center, 2002–2015

Context: Mercury exposure has been described among small-scale gold mining communities in developing countries, but reports of inhalational mercury toxicity among home gold extractors in the US remain uncommon.Objective: We sought to identify inhalational mercury exposures and toxicity among artisanal gold extractors.Methods: This is an observational case series of a single Poison Center database from 2002–2015. We review all cases of “mercury” or “mercury inhalation” exposures, with detailed description of a recent representative case.Results: Nine cases were reported, with patients’ ages ranging 32–81 years. Eight (89%) patients were male. Seven of eight (88%) patients with acute exposures reported pulmonary symptoms consistent with mercury vapor inhalation such as dyspnea and cough; two (29%) patients had severe toxicity requiring intubation. Four of six (67%) patients had markedly elevated whole blood mercury concentrations up to 346 mcg/L; each received a different chelation regimen. Four (44%) patients used methamphetamines at the time of their exposure. The case report describes a patient with elevated mercury concentrations who required intubation for hypoxic respiratory failure. He received chelation therapy based on chelator availability, with decreasing 24-hour urine mercury concentrations. The house where he was exposed remains uninhabitable from elevated ambient mercury vapor concentrations.Conclusion: Artisanal gold extraction may be associated with inhalational mercury toxicity, including elevated blood mercury concentrations and acute hypoxic lung injury requiring intubation.

Evaluation of Etanercept Treatment in Newborn Rat Model with Hyperoxic Lung Injury

ABSTRACTBackground: Many factors contribute to the development of BPD basically by increasing inflammation in preterm lungs. However, premature neonates have insufficient anti-inflammatory capacity. We aimed to evaluate the effect of etanercept, an anti-TNF agent, on BPD development in newborn rat model with hyperoxia-induced lung injury. Methods: Thirty-two newborn rats were divided into 3 groups as control group (Group 1, n = 11), hyperoxia + placebo group (Group 2, n = 10), and hyperoxia + etanercept group (Group 3, n = 11). Histopathological and biochemical analysis were performed in order to assess inflammation and oxidative stress. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities, and malondialdehyde (MDA) levels were studied, histopathological scoring and radial alveolar count were applied in lung tissue. Lamellar body membrane protein, vascular endothelial growth factor (VEGF), nuclear factor-kappaB (NF-κB) gene expressions were studied in immunohistochemical evaluation of tissue samples. All three groups were compared with each other in terms of all parameters. Results: SOD and GSH-Px activities were significantly higher, whereas MDA levels were lower in group 3, compared to group 2 (p < 0.001). Histopathological scores were lower, lamellar body membrane protein expression and radial alveolar count were higher in group 3 (p < 0.05). NF-κB expression was higher in group 2, but lower in group 3 in comparison with group 1. Expression of VEGF was decreased in group 2 but came close to group 1 with etanercept treatment in group 3. Conclusions: We found etanercept treatment to be protective in newborn rats with hyperoxia-induced lung damage.

Placental Growth Factor Triggers Epithelial-to-Mesenchymal Transition-like Changes in Rat Type II Alveolar Epithelial Cells: Activation of Nuclear Factor κB Signalling Pathway.

Epithelial-to-mesenchymal transition (EMT) occurs frequently in lung epithelium in response to damage stimuli, such as inflammation and oxidative stress. Our group has already found an excessive release of placental growth factor (PLGF) in hyperoxic lung injury in newborn rodents. Nonetheless, whether this increased PLGF plays a role in mediating EMT process of alveolar epithelial cells (AECs) is unclear and requires further investigation. In this study, primary type II AECs were first isolated for neonatal Sprague Dawley (SD) rats and treated with different doses (25 or 100 ng/ml) of recombinant PLGF for 48 hr. As compared to the untreated AECs, exogenous PLGF induced a reduction in E-cadherin (a critical epithelial maker) and increases in vimentin and fibronectin (mesenchymal markers) in a dose-dependent manner. The higher dose was more potent in promoting the EMT-like changes in AECs. We also found that PLGF promoted the degradation of nuclear factor κB (NFκB) inhibitor (IκBα), induced phosphorylation of NFκB p65 at Ser 536 and enhanced p65 nuclear translocation in primary AECs. In addition, the NFκB inhibitor BAY 11-7082 partly counteracted PLGF-induced alterations in EMT-related proteins in rat AECs. In summary, our study demonstrates that exogenous PLGF can induce EMT-like changes in type II AECs at least partly by activating NFκB signalling transduction in vitro. PLGF may play a role in driving fibrotic lesions and thus can be a promising target for lung diseases.

Mechanistic role of cytochrome P450 (CYP)1B1 in oxygen-mediated toxicity in pulmonary cells: A novel target for prevention of hyperoxic lung injury

Supplemental oxygen, which is routinely administered to preterm infants with pulmonary insufficiency, contributes to bronchopulmonary dysplasia (BPD) in these infants. Hyperoxia also contributes to the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) in adults. The mechanisms of oxygen-mediated pulmonary toxicity are not completely understood. Recent studies have suggested an important role for cytochrome P450 (CYP)1A1/1A2 in the protection against hyperoxic lung injury. The role of CYP1B1 in oxygen-mediated pulmonary toxicity has not been studied. In this investigation, we tested the hypothesis that CYP1B1 plays a mechanistic role in oxygen toxicity in pulmonary cells in vitro. In human bronchial epithelial cell line BEAS-2B, hyperoxic treatment for 1–3 days led to decreased cell viability by about 50–80%. Hyperoxic cytotoxicity was accompanied by an increase in levels of reactive oxygen species (ROS) by up to 110%, and an increase of TUNEL-positive cells by up to 4.8-fold. Western blot analysis showed hyperoxia to significantly down-regulate CYP1B1 protein level. Also, there was a decrease of CYP1B1 mRNA by up to 38% and Cyp1b1 promoter activity by up to 65%. On the other hand, CYP1B1 siRNA appeared to rescue the cell viability under hyperoxia stress, and overexpression of CYP1B1 significantly attenuated hyperoxic cytotoxicity after 48 h of incubation. In immortalized lung endothelial cells derived from Cyp1b1-null and wild-type mice, hyperoxia increased caspase 3/7 activities in a time-dependent manner, but endothelial cells lacking the Cyp1b1 gene showed significantly decreased caspase 3/7 activities after 48 and 72 h of incubation, implying that CYP1B1 might promote apoptosis in wild type lung endothelial cells under hyperoxic stress. In conclusion, our results support the hypothesis that CYP1B1 plays a mechanistic role in pulmonary oxygen toxicity, and CYP1B1-mediated apoptosis could be one of the mechanisms of oxygen toxicity. Thus, CYP1B1 could be a novel target for preventative and/or therapeutic interventions against BPD in infants and ALI/ARDS in adults.

Sirtuin 1 Promotes Hyperoxia-Induced Lung Epithelial Cell Death Independent of NF-E2-Related Factor 2 Activation.

Lung epithelial cell damage accompanied by death is a cardinal feature of toxicant- and prooxidant-induced acute lung injury. The transcription factor nuclear factor (erythroid-derived 2)-like 2 (NEF2L2 or NRF2) activates several antioxidant enzymes (AOEs) and prosurvival genes in response to oxidant stress, and its deficiency enhances susceptibility to hyperoxic lung injury and other oxidant-induced lung pathologies. Sirtuin 1 (SIRT1) regulates cell growth and survival in response to both physiological and pathological stresses by selectively deacetylating multiple proteins required for chromatin remodeling and transcription; therefore, we sought to examine potential SIRT1-NRF2 cross-talk in the regulation of AOE expression during hyperoxia-induced lung epithelial cell death. Unexpectedly, pharmacological inhibition or small interfering RNA-mediated depletion of SIRT1 caused a reduction in cell death, accompanied by reduced levels of NRF2-dependent AOE expression in chronic hyperoxia. NRF2 acetylation was markedly and transiently higher in cells exposed to acute (6 h) hyperoxia. Sirtinol blocked this acute effect, but NRF2 acetylation was low or undetectable in cells exposed to chronic hyperoxia (24-36 h) both with and without sirtinol. SIRT1 activation by resveratrol augmented hyperoxia-induced death in cells with NRF2 deficiency. SIRT1 inhibition or depletion led to a reduced activation of the cell-death executioner caspase 3, whereas caspase inhibition prevented death. Consistent with these results, sirtinol attenuated hyperoxia-induced lung alveolar permeability and toxicity in vivo. Collectively, these results reveal that, in chronic hyperoxia, SIRT1 promotes hyperoxia-induced lung epithelial cell damage and death by altering pro- and antiapoptotic balance, not by dampening optimal NRF2-dependent AOE expression.

Gene Expression Profiling Identifies Cell Proliferation and Inflammation as the Predominant Pathways Regulated by Aryl Hydrocarbon Receptor in Primary Human Fetal Lung Cells Exposed to Hyperoxia.

Exposure to hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. We observed that aryl hydrocarbon receptor (AhR) signaling protects newborn mice and primary fetal human pulmonary microvascular endothelial cells (HPMECs) against hyperoxic injury. Additionally, a recent genome-wide transcriptome study in a newborn mouse model of BPD identified AhR as a key regulator of hyperoxia-induced gene dysregulation. Whether the AhR similarly deregulates genes in HPMEC is unknown. Therefore, the objective of this study was to characterize transcriptome level gene expression profile in AhR-sufficient and -deficient HPMEC exposed to normoxic and hyperoxic conditions. Global gene expression profiling was performed using Illumina microarray platform and selected genes were validated by real-time RT-PCR. AhR gene expression and hyperoxia independently affected the expression of 540 and 593 genes, respectively. Two-way ANOVA further identified 85 genes that were affected by an interaction between AhR expression and exposure to hyperoxia. Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology, and Reactome pathway analysis identified cell proliferation, immune function, cytokine signaling, and organ development as the major pathways affected in AhR-deficient cells. The biological processes that were significantly enriched by hyperoxia included metabolic process, stress response, signal transduction, cell cycle, and immune regulation. Cell cycle was the predominant pathway affected by the combined effect of AhR knockdown and hyperoxia. Functional analysis of cell cycle showed that AhR-deficient cells had decreased proliferation compared with AhR-sufficient cells. These findings suggest that AhR modulates hyperoxic lung injury by regulating the genes that are necessary for cell proliferation and inflammation.

Intratracheal transplantation of mesenchymal stem cells simultaneously attenuates both lung and brain injuries in hyperoxic newborn rats.

Bronchopulmonary dysplasia is an independent risk factor for adverse neurodevelopmental outcomes in premature infants. We investigated whether attenuation of hyperoxic lung injury with intratracheal transplantation of human umbilical cord blood-derived mesenchymal stem cells (MSCs) could simultaneously mitigate brain damage in neonatal rats. Newborn Sprague-Dawley rats were exposed to hyperoxia or normoxia conditions for 14 d. MSCs (5 × 10(5) cells) were transplanted intratracheally at postnatal day (P) 5. At P14, lungs and brains were harvested for histological and biochemical analyses. Hyperoxic lung injuries, such as impaired alveolarization evident from increased mean linear intercept (MLI) and elevated inflammatory cytokine levels were significantly alleviated with MSC transplantation. Hyperoxia decreased brain weight, increased brain cell death, and induced hypomyelination. MSC transplantation significantly ameliorated hyperoxia-induced increased terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells in the dentate gyrus and reduced myelin basic protein. In correlation analyses, brain weight and myelin basic protein (MBP) were significantly inversely correlated with lung MLI and inflammatory cytokines, while TUNEL-positive brain cell number showed a significant positive correlation with lung MLI. Despite no significant improvement in short-term neurofunctional outcome, intratracheal transplantation of MSCs simultaneously attenuated hyperoxic lung and brain injuries in neonatal rats, with the extent of such attenuation being closely linked in the two tissues.

VEGF-D promotes pulmonary oedema in hyperoxic acute lung injury.

Leakage of fluid from blood vessels, leading to oedema, is a key feature of many diseases including hyperoxic acute lung injury (HALI), which can occur when patients are ventilated with high concentrations of oxygen (hyperoxia). The molecular mechanisms driving vascular leak and oedema in HALI are poorly understood. VEGF‐D is a protein that promotes blood vessel leak and oedema when overexpressed in tissues, but the role of endogenous VEGF‐D in pathological oedema was unknown. To address these issues, we exposed Vegfd‐deficient mice to hyperoxia. The resulting pulmonary oedema in Vegfd‐deficient mice was substantially reduced compared to wild‐type, as was the protein content of bronchoalveolar lavage fluid, consistent with reduced vascular leak. Vegf‐d and its receptor Vegfr‐3 were more highly expressed in lungs of hyperoxic, versus normoxic, wild‐type mice, indicating that components of the Vegf‐d signalling pathway are up‐regulated in hyperoxia. Importantly, VEGF‐D and its receptors were co‐localized on blood vessels in clinical samples of human lungs exposed to hyperoxia; hence, VEGF‐D may act directly on blood vessels to promote fluid leak. Our studies show that Vegf‐d promotes oedema in response to hyperoxia in mice and support the hypothesis that VEGF‐D signalling promotes vascular leak in human HALI. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Deletion of ASK1 Protects against Hyperoxia-Induced Acute Lung Injury.

Apoptosis signal-regulating kinase 1 (ASK1), a member of the MAPK kinase kinase kinase (MAP3K) family, is activated by various stimuli, which include oxidative stress, endoplasmic reticulum (ER) stress, calcium influx, DNA damage-inducing agents and receptor-mediated signaling through tumor necrosis factor receptor (TNFR). Inspiration of a high concentration of oxygen is a palliative therapy which counteracts hypoxemia caused by acute lung injury (ALI)-induced pulmonary edema. However, animal experiments so far have shown that hyperoxia itself could exacerbate ALI through reactive oxygen species (ROS). Our previous data indicates that ASK1 plays a pivotal role in hyperoxia-induced acute lung injury (HALI). However, it is unclear whether or not deletion of ASK1 in vivo protects against HALI. In this study, we investigated whether ASK1 deletion would lead to attenuation of HALI. Our results show that ASK1 deletion in vivo significantly suppresses hyperoxia-induced elevation of inflammatory cytokines (i.e. IL-1β and TNF-α), cell apoptosis in the lung, and recruitment of immune cells. In summary, the results from the study suggest that deletion of ASK1 in mice significantly inhibits hyperoxic lung injury.

Dose-dependent effects of glucocorticoids on pulmonary vascular development in a murine model of hyperoxic lung injury.

BACKGROUNDExposure of neonatal mice to hyperoxia results in pulmonary vascular remodeling and aberrant phosphodiesterase-5 (PDE5) signaling. Although glucocorticoids are frequently utilized in the NICU, little is known about their effects on the developing pulmonary vasculature and on PDE5. We sought to determine the effects of hydrocortisone (HC) on pulmonary vascular development and on PDE5 in a neonatal mouse model of hyperoxic lung injury.METHODSC57BL/6 mice were placed in 21% O2 or 75% O2 within 24h of birth and received HC (1, 5, or 10 mg/kg subcutaneously every other day) or vehicle. At 14d, right ventricular hypertrophy (RVH), medial wall thickness (MWT), lung morphometry, and pulmonary artery (PA) PDE5 activity were assessed. PDE5 activity was measured in isolated pulmonary artery smooth muscle cells (PASMC) exposed to 21% or 95% O2 ± 100nM HC for 24h.RESULTSHyperoxia resulted in alveolar simplification, RVH, increased MWT, and increased PA PDE5 activity. HC decreased hyperoxia-induced RVH and attenuated MWT. HC had dose-dependent effects on alveolar simplification. HC decreased hyperoxia-induced PDE5 activity in vivo and in vitro.CONCLUSIONSHC decreases hyperoxia-induced pulmonary vascular remodeling and attenuates PDE5 activity. These findings suggest that HC may protect against hyperoxic injury in the developing pulmonary vasculature.

Nitric oxide and hyperoxic acute lung injury

Hyperoxic acute lung injury (HALI) refers to the damage to the lungs secondary to exposure to elevated oxygen partial pressure. HALI has been a concern in clinical practice with the development of deep diving and the use of normobaric as well as hyperbaric oxygen in clinical practice. Although the pathogenesis of HALI has been extensively studied, the findings are still controversial. Nitric oxide (NO) is an intercellular messenger and has been considered as a signaling molecule involved in many physiological and pathological processes. Although the role of NO in the occurrence and development of pulmonary diseases including HALI has been extensively studied, the findings on the role of NO in HALI are conflicting. Moreover, inhalation of NO has been approved as a therapeutic strategy for several diseases. In this paper, we briefly summarize the role of NO in the pathogenesis of HALI and the therapeutic potential of inhaled NO in HALI.

Protective effect of C4a against hyperoxic lung injury via a macrophage-dependent but not a neutrophil/lymphocyte-dependent signaling pathway.

Complement anaphylatoxins have been investigated extensively; however, the role of complement anaphylatoxin C4a in hyperoxic lung injury has yet to be investigated. To the best of our knowledge, the present study is the first to demonstrate the role of C4a in hyperoxic lung injury in vitro and in vivo. BALB/c mice were ventilated with 100% oxygen with or without C4a treatment for 36 h. The body weight and the relative lung weight of the mice were determined, along with any morphological changes in the lung. The expression levels of interleukin (IL)-1, IL-6 and tumor necrosis factor-α (TNF-α) were quantified in the lung tissue and bronchoalveolar lavage fluid (BALF) samples by enzyme-linked immunosorbent assay (ELISA) and western blot analysis. The total cell count and the number of macrophages, neutrophils and lymphocytes in the BALF were determined using cytocentrifuge slides and a hemocytometer. Histamine release from total cells in the BALF was also analyzed. The relative mRNA expression levels of CD68, F4/80, CD64, CD19 and CD3 in the murine lung tissue were assessed by reverse transcription-quantitative polymerase chain reaction. The results revealed that hyperoxia induced lung injury and morphological changes, and increased the expression levels of IL-1, IL-6 and TNF-α, histamine release, the number of inflammatory cells, and the expression levels of CD68, F4/80, CD64, CD19 and CD3. The hyperoxia-induced morphological changes and inflammatory reaction were significantly attenuated in mice treated with C4a. Treatment with C4a also attenuated the increase in the total cell count, decreased the number of macrophages in the BALF, and suppressed the elevated mRNA expression levels of CD68 and F4/80 in the lung tissue samples. Conversely, treatment with C4a did not affect the number of neutrophils or lymphocytes in the BALF or the mRNA expression of CD64, CD19 and CD3 in lung tissue. In conclusion, C4a attenuated hyperoxic lung injury via a macrophage-dependent but not a neutrophil/lymphocyte-dependent pathway.

Lung Damage and Thrombocytopenia

Hematological changes in patients with lung damage were common and included thrombocytopenia (55%) (Yang et al, Int J Mol Med. 2004; Hon et al, Lancet. 2003). A number of potential mechanisms have been investigated. The lungs of patients who died of lung infection show diffuse alveolar damage with pulmonary congestion, edema, formation of hyaline membrane, and fibrosis. Viral infection, oxygen toxicity and/or barotrauma contribute to the lung damage. The lung tissue and pulmonary endothelial cell damage result in platelet activation, aggregation, and thrombi formation at the site of the injury. All these mechanisms may induce the consumption of platelets and megakaryocytes (MK). The association between lung injury and thrombocytopenia was investigated by comparing the MK and platelet counts, and platelet activation using P-selectin as a marker, between the prepulmonary (right atrial) and postpulmonary (left atrial) blood in rats with and without hyperoxic lung injury. In the healthy controls, the postpulmonary blood had lower megakaryocyte count, higher platelet count, but similar P-selectin expression. In contrast, the lung-damaged animals did not show any such differences in either MK or platelet count, but P-selectin expression was greater in the postpulmonary blood. Peripheral platelet and intra-pulmonary MK counts in the lung-damaged rats were significantly lower than those in their respective controls. Intra-pulmonary thrombi or platelet aggregation were detected in the lung-damaged rats but not in the controls. These findings showed that lung damage reduced circulating platelets through (i) failure of the lungs to retain and fragment MK to release platelets, (ii) and platelet activation leading to platelet aggregation, thrombi formation and platelet consumption. The number and morphology of circulating MK were also investigated before, during and after cardiopulmonary bypass (CPB) in 22 patients undergoing routine cardiac surgery. Results showed that: (i) The total number of MK in central venous was higher than those of peripheral arteries during normal circulation (P<0.01). There was significant decrease of Type-4 MK (mature and large MK) number in peripheral arteries compared with that in central venous (P<0.001); and (ii) During CPB, the total MK and Type-4 MK of central venous and peripheral arteries were significant increased when compared with that in normal circulation (P<0.01). Our observation supports that the lungs may remove large MK during normal circulation. This physiological effect would be lost on CPB. On the other hand, the lungs may be the sites of platelet release from mature MK. The inflammation, the long term ventilation and/or oxygen therapy may result in pulmonary fibrosis and other pathological changes. The reduced or morphologically altered pulmonary capillary bed would affect the MK fragmentation in the lung. The increased consumption of platelet and/or the decreased production of platelet may lead to thrombocytopenia. DisclosuresYang:National Natural Science Foundation of China(81270580): Research Funding.

Growth differentiation factor-15/macrophage inhibitory cytokine-1 induction after kidney and lung injury.

The immunoregulatory cytokine macrophage inhibitory cytokine-1 (MIC-1), a divergent TGF-beta family member, and its murine ortholog, growth/differentiation factor-15 (GDF-15) are induced in hepatocytes by surgical and chemical injury and heat shock. To better understand the in vivo role this factor plays in organ injury, we examined the regulation of GDF-15 in murine models of kidney and lung injury. We demonstrate herein induction of GDF-15/MIC-1 after surgical, toxic/genotoxic, ischemic, and hyperoxic kidney or lung injury. Gdf15 induction was independent of protein synthesis, a hallmark of immediate-early gene regulation. Although TNF induced GDF-15 expression, injury-elicited Gdf15 expression was not reduced in mice deficient for both TNF receptor subtype. Furthermore, although the stress sensor p53 is known to induce GDF-15/MIC-1 expression, injury-elicited Gdf15 expression was unchanged in p53-null mice. Our results demonstrate that GDF-15 induction after organ injury is a hallmark of many tissues. These data demonstrate that GDF-15/MIC-1 is an early mediator of the injury response in kidney and lung that might regulate inflammation, cell survival, proliferation, and apoptosis in a variety of injured tissues and disease processes.

Nanoparticle facilitated inhalational delivery of erythropoietin receptor cDNA protects against hyperoxic lung injury

Our goals were to develop and establish nanoparticle (NP)-facilitated inhalational gene delivery, and to validate its biomedical application by testing the hypothesis that targeted upregulation of pulmonary erythropoietin receptor (EpoR) expression protects against lung injury. Poly-lactic-co-glycolic acid (PLGA) NPs encapsulating various tracers were characterized and nebulizated into rat lungs. Widespread NP uptake and distribution within alveolar cells were visualized by magnetic resonance imaging, and fluorescent and electron microscopy. Inhalation of nebulized NPs bearing EpoR cDNA upregulated pulmonary EpoR expression and downstream signal transduction (ERK1/2 and STAT5 phosphorylation) in rats for up to 21days, and attenuated hyperoxia-induced damage in lung tissue based on apoptosis, oxidative damage of DNA, protein and lipid, tissue edema, and alveolar morphology compared to vector-treated control animals. These results establish the feasibility and therapeutic efficacy of NP-facilitated cDNA delivery to the lung, and demonstrate that targeted pulmonary EpoR upregulation mitigates acute oxidative lung damage. From the Clinical EditorAcute lung injury often results in significant morbidity and mortality, and current therapeutic modalities have proven to be ineffective. In this article, the authors developed nanocarrier based gene therapy in an attempt to upregulate the expression of pulmonary erythropoietin receptor in an animal model. Inhalation delivery resulted in reduction of lung damage.